// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_BASE_AUDIO_PULL_FIFO_H_
#define MEDIA_BASE_AUDIO_PULL_FIFO_H_

#include <memory>

#include "base/callback.h"
#include "base/macros.h"
#include "media/base/media_export.h"

namespace media {
class AudioBus;

// A FIFO (First In First Out) buffer to handle mismatches in buffer sizes
// between a producer and consumer. The consumer will pull data from this FIFO.
// If data is already available in the FIFO, it is provided to the consumer.
// If insufficient data is available to satisfy the request, the FIFO will ask
// the producer for more data to fulfill a request.
class MEDIA_EXPORT AudioPullFifo {
public:
    // Callback type for providing more data into the FIFO.  Expects AudioBus
    // to be completely filled with data upon return; zero padded if not enough
    // frames are available to satisfy the request.  |frame_delay| is the number
    // of output frames already processed and can be used to estimate delay.
    typedef base::Callback<void(int frame_delay, AudioBus* audio_bus)> ReadCB;

    // Constructs an AudioPullFifo with the specified |read_cb|, which is used to
    // read audio data to the FIFO if data is not already available. The internal
    // FIFO can contain |channel| number of channels, where each channel is of
    // length |frames| audio frames.
    AudioPullFifo(int channels, int frames, const ReadCB& read_cb);
    virtual ~AudioPullFifo();

    // Consumes |frames_to_consume| audio frames from the FIFO and copies
    // them to |destination|. If the FIFO does not have enough data, we ask
    // the producer to give us more data to fulfill the request using the
    // ReadCB implementation.
    void Consume(AudioBus* destination, int frames_to_consume);

    // Empties the FIFO without deallocating any memory.
    void Clear();

    // Returns the size of the fifo in number of frames.
    int SizeInFrames() const;

private:
    // Attempt to fulfill the request using what is available in the FIFO.
    // Append new data to the |destination| starting at |write_pos|.
    int ReadFromFifo(AudioBus* destination, int frames_to_provide, int write_pos);

    // Source of data to the FIFO.
    const ReadCB read_cb_;

    // Temporary audio bus to hold the data from the producer.
    std::unique_ptr<AudioBus> fifo_;
    int fifo_index_;

    DISALLOW_COPY_AND_ASSIGN(AudioPullFifo);
};

} // namespace media

#endif // MEDIA_BASE_AUDIO_PULL_FIFO_H_
